A wide-ranging new analysis of Congressional floor speeches finds that political polarization has “exploded” over the past 20 years, and is now “far greater today than at any point in the past.”

The study, by economists at Stanford and Brown universities and the University of Chicago, analyzed the entirety of the congressional record going back to 1873. The researchers built a sophisticated model capable of measuring how easy it would be for a typical listener to guess a speaker’s political party based on the words the speaker used in one minute of speech.

The results were striking: from the 1870s until roughly 1990, “partisanship was low and roughly constant,” according to the analysis of congressional language. In most years during that time period, a listener would have a little more than a 50 percent chance of “correctly guessing a speaker’s party based on a one-minute speech.”

But in recent years political language has changed dramatically. “Beginning with the congressional election of 1994, partisanship turned sharply upward, with the probability of guessing correctly based on a one-minute speech climbing to 83 percent by the 110th session (2007-09).”

To conduct the analysis, the researchers looked for “partisan phrases” — phrases whose removal from a speech would make it harder to infer a speaker’s political leanings. Those phrases have changed greatly over time.

In the late 1800s, hot-button phrases were related to discussions of tariffs and protectionism, such as “tariff tax,” “increase duties” or “fisheries treaty.” These were phrases that showed up in party platforms relating to the big political debates of the day.

By the late 1960s, Democrats were aggressively trying to expand the federal safety net. Phrases like “food stamps” and “school lunch” carried highly partisan connotations. And by the mid-2000s, the partisan contours of our present-day political fights come into focus. Phrases like “illegal immigrant” and “higher taxes” …